When operating internal combustion engines and hydraulic-mechanical devices, lubricating oil and hydraulic oil, respectively, is used. Internal combustion engines can run on liquid fuel such as e.g. petrol or diesel oil. When the internal combustion engine is operated, the lubricating oil that lubricates the engine becomes contaminated with non-combusted fuel, water, refrigerant and substances from the fuel combustion. Hydraulic oil is contaminated in a similar way but is not subject to any combustion process but on the other hand subject to the oil absorbing water from air humidity and condensation in the tank or from water penetrating the system at changeovers or when cleaning.
There is a desire to clean the oil from unwanted substances without needing to change the oil in the device.
In U.S. Pat. No. 6,083,406 and U.S. Pat. No. 5,707,515 a method and a device, respectively, for cleaning lubricating oil in an internal combustion engine is shown. The device comprises a particle filter that initially cleans the oil from particles and a liquid separation part intended for separating liquid in the form of water and fuel from the particle free oil. The liquid separation part comprises a substantially dome shaped heat plate. In one embodiment the dome shaped heat plate comprises a flat top and a number of, in a stair shaped structure below each other, slanted flat surfaces connected with elevations. The functioning of the device is as follows:
The particle free but from other liquids contaminated oil is sprinkled over the top of the dome shaped heat plate, after which the oil is supposed to, with the help of gravitation, to flow in a film along the sides of the heat plate, e.g. along the slanted flat surfaces of the heat plate. The function of the elevations is to stop the flow of oil in order for the oil to remain on the heat plate for a certain period.
The heat plate is manufactured of heat conductive material such as aluminium and is evenly heated by a thermostatically controlled heating coil. The complete oil film is brought to a temperature, by the heat plate, where the liquid can “boil” off from the oil which remains on the plate.
The evaporated liquid is captured and brought back to the combustion chamber and the cleaned oil is brought back to the engine, e.g. to a oil container or oil tray.
The method disclosed in U.S. Pat. No. 6,083,406 and the device in U.S. Pat. No. 5,707,515 both have a number of drawbacks.
The oil leaving the particle filter has a temperature of approximately 90° C. which means that the oil sprinkled over the heat plate can have a maximum temperature of approximately 90° C. Diesel oil has a boiling point at 250° C.-300° C. and lubricating oil has a considerably higher boiling point. The lubricating oil is however temperature sensitive but can be exposed to relatively high temperatures above 140° C., but only for a short period. Even if the diesel oil does not reach its boiling point, the diesel oil is partly evaporated at a lower temperature with an increasing degree dependent on increasing temperature. To achieve a maximum evaporation of diesel oil the temperature of the lubricating oil should therefore be increased to a maximum which the lubricating oil can withstand. The lubricating oil can withstand a high temperature for a short period better than a low temperature for a long period. The worst alternative is however high temperature under a long period as the oil is oxidized and destroyed.
The heat plate according to U.S. Pat. No. 6,083,406 and U.S. Pat. No. 5,707,515 aim at, through the use the elevations, to stop the flow of oil in order that all oil should have time to be heated to a certain temperature and in this way be able to “boil” off the contamination over the complete surface of the plate. This is a drawback as a high flow of oil is aimed at to achieve cleaning of big quantities of oil per unit of time. At the same time the low flow gives a long dwell time for the oil on the hot plate.
An example of a suitable oil flow is 0.65 l/minute. To be able to heat the oil from 90° C. to approximately 140° C. at this flow rate the oil needs an addition of 1 Kilowatt. The heat plate according to U.S. Pat. No. 6,083,406 and U.S. Pat. No. 5,707,515 is not capable of handling flows in this order, but is limited to a lower flow to give the desired temperature increase, with the result that the oil is destroyed because of the long dwell time. If the flow was allowed to increase, the temperature of the whole heat plate would need to be increased for the oil to have time to be heated. Higher temperature makes however the oil at the edges, where the oil has the slowest flow, running the risk of getting burnt and stuck and/or be destroyed through oxidization. Thus the method and device according to U.S. Pat. No. 6,083,406 and U.S. Pat. No. 5,707,515 are limited to low flow rates only. The low flow rate means that the oil circulation becomes too low to be able to achieve an effective cleaning process as the object is to clean all oil in the lubricating system of the engine.
The problem area is also made worse because of the fact that the outdoor temperature differs in different climates in different parts of the world, which affects the temperature of the oil entering the liquid separation part. Cold conditions give colder oil and further energy is therefore required in order for the oil to reach the right temperature. Warm conditions give warmer oil requiring the heat from the heat plate to be regulated to compensate the heat increase in order for the oil not to reach too high temperature and be destroyed. A properly working regulating arrangement for the heat plate is thus necessary for a properly working system. Such a regulating arrangement comprises thermostats and other regulators comprising moving parts which in this delicate context is a possible cause for malfunction causing limited useful life, and causing destroying high oil temperatures. Such a regulating arrangement is also expensive and hard to install.
Further problems with the device are that the heat plate has to be located horizontally in order for the oil, supplied from above, with the help of gravitation should be evenly distributed over the plate and in this way create a thin film. Problems are also encountered when the engine changes position, e.g. when a vehicle is driven in a curve. The cause for this being the change of the engine position causing change of the position of the device. The oil is also subject to a side force when it is sprinkled towards the liquid separation part. Both the change of position and the side force causes an uneven distribution of the oil over the heat plate as the gravitation alone can not distribute the oil evenly at said conditions. The device is thus limited to a horizontal position and can not be installed in another angle than 180° towards gravitation and can not be used at optimum in a vehicle used in curves and hills.
Hydraulic oil contaminated with water has analogue problems. The boiling point of water is 100° C. and the hydraulic oil has a maximum temperature of 80° C., but a working temperature of approximately 50° C. The oil has to be heated as much as it can take during as short period as possible to give the best evaporation of water at as high flow rate as possible. Also in this case it is a problem with the homogeneously heated heat plate which is limited to low flow rates for the same reason as mentioned above.
Thus, there is a desire for an improved device and an improved method for regeneration of oil in an internal combustion engine. Over and above this there is in the same way a desire for an improved regeneration of hydraulic oil.